On Tuesday, June 25, 2002, at 04:01  PM, Phillip S. Baker wrote:

> Yes I knew it was Javascript code, but I also thought PHP was needed to 
> get the values from the DB.
> Either case I do need help with what the code might look like.

Okay, here it is... kinda complicated, but using this theory you should 
be able to do it:

You need to populate an HTML listbox based on DB data.  Make sure your 
SELECT query gets both the primary key of each record and the actual 
name that you want to appear in the listbox.  Dynamically generate the 
listbox in the normal way, by using the primary key as the "value" 
attribute of each <option> tag and using the other column value as the 
CDATA contents of the option element, like this:

$sql = "SELECT id, name FROM table";
$result = mysql_query($sql, $db);
$output = '';
while ($row = mysql_fetch_assoc($result)) {
        $output .= "\t<option value=\"" . $row['id']
                        . "\" onselect\"controlOther(" . $row['id']
                        . ")\">" . $row['name']
                        . "</option>\n";

You will have something like this in $output:

        <option value="1" onselect="controlOther(1)">Yoda</option>
        <option value="2" onselect="controlOther(2)">Ben</option>
        <option value="3" onselect="controlOther(3)">Annikin</option>
        <option value="4" onselect="controlOther(4)">Luke</option>

The "controlOther()" is a JavaScript function that you will write in a 

Anyway, you now have a listbox with values that exactly match your 
JavaScript array.  What you do next is you assign a name to the select 
tag which holds the listbox values, and place the listbox values into 
the select tag:

$selectTag = "<select name='jedimasters'>" . $output . "</select>\n";

And of course you need to put your select tag into a named form (the 
names are important for the JavaScript!):

$form = "       <form method=\"" . $_SERVER['PHP_SELF'] . "\" 
                        BLAH BLAH BLAH other inputs can go here
                        " . $selectTag . "

Okay!  Now you have your form, named "choosejedi", your input, named 
"jedimasters", and a listbox filled with name/value pairs.  Your 
intended effect is to allow one listbox's actions to control another 
listbox's data.  For this, you need to write a JavaScript function that 
controls the other listbox.

$coFunc = "     <script type='text/javascript'>
                                function controlOther(choice)
                                        var contents = '';
                                        switch(choice) {
                                                case 1:
                                                        contents = AAAA;
                                                case 2:
                                                        contents = BBBB;
                                                case 3:
                                                        contents = CCCC;
                                                case 4:
                                                        contents = DDDD;
                                                        alert('Invalid value 
                                        } // end switch()

You can see what this function does -- it takes the value of the 
argument passed to it and executes certain other code according to the 
switch() statement.  I don't have time to actually write out possible 
code for these cases, so I just put "AAAA" or "BBBB" etc (it's all a 
hypothetical example anyway).  You will want to have already generated 
this data from the DB using PHP anyway, so you would just plug in a few 
variables here (whose values are defined earlier in the script).

The point is that every time someone makes a selection in the listbox, 
they will trigger the ONSELECT event handler, which calls the 
"controlOther()" JavaScript function.  The value passed to 
controlOther() tells ANOTHER listbox on the page what it should be 
populated with, based on the switch() statement.  You need to have names 
for all your forms and your inputs so that you can refer to them using 
the JavaScript Document Object Model... in other words, your controlling 
code would look something like


refers to the selected value in the main listbox, and can be used to 
perform actions on other listboxes.

ANYWAY... this got way longer than I intended.  Basically, I haven't 
tested any of the above but in theory it should work, but be sure to do 
mad browser detection so you can be sure that it'll work, etc.  I 
personally wouldn't even bother, this kind of coding is pretty technical 
and you may as well just do it in PHP in case the user doesn't have JS 
turned on.  I think it's a lot easier to do it in PHP too.  Sure, the 
user will have to submit the page to update the new listbox, but... not 
so hard, eh?  Essentially it boils down to this pseudocode:

1. use PHP to dynamically generate a main listbox to control the next 
2. use PHP to dynamically generate possible values for the secondary 
listbox (I would just throw 'em in arrays)
3. determine which array should populate the second listbox based on the 
input in the first listbox using JavaScript event handlers in the first 




Erik Price
Web Developer Temp
Media Lab, H.H. Brown

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